


Our Little Secret

by thewinchesterlifestyle



Category: Supernatural
Genre: Age Difference, Bottom Castiel, Castiel and Dean Winchester are Siblings, Castiel is a Winchester, Dirty Talk, Fingering, M/M, Name Calling, Older Sibling Dean Winchester, Rough Sex, Sibling Incest, Size Difference, Size Kink, Spanking, Teen Castiel, Top Dean Winchester, Underage - Freeform, Younger Sibling Castiel (Supernatural), putting dubcon cause cas is underage
Language: English
Status: Completed
Published: 2016-07-22
Updated: 2016-07-22
Packaged: 2018-07-26 03:22:58
Rating: Not Rated
Warnings: Underage
Chapters: 1
Words: 1,915
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7558243
Author URL: https://archiveofourown.org/users/thewinchesterlifestyle/pseuds/thewinchesterlifestyle
Summary: <blockquote class="userstuff">
              <p>Dean always waits until everyone is asleep in the house before sneaking down the hallway into his little brother's room. He's been doing this for years and his parents had yet to catch him with Castiel.</p>
            </blockquote>





	Our Little Secret

**Author's Note:**

> This is a brothers AU where Castiel is in fact Dean's youngest brother (Sam is still his brother of course).

Dean rolled over and glanced at the clock. Three in the morning. A slow smile tugged at his lips as he climbed out of bed, collected his bottle of lube and padded out of his room. The house was silent this time of the morning as his parents and his brothers slept.

He was careful to avoid the places in the hallway that creaked as he made his way to Castiel’s room and silently eased the door open. His younger brother’s room was dark save for the faint light coming from the window that gave him a good view of Castiel sprawled out in his bed.

The door shut softly behind him. For a moment Dean paused before crossing the room and looking down at Castiel’s sleeping form. His brother’s face was slack with sleep and a hand clutched at his pillow.

Dean set the bottle of lube down on the bed, reached for his boxers and tugged them off. He could feel the steady thrum of arousal in his veins and how his cock hardened in anticipation.

It had been a few days since he’d snuck into Castiel’s room for this very purpose and the thought of pushing into Castiel’s tight little ass, of fucking his youngest brother into the mattress, nearly had him moaning out loud.

Instead he moved the lube and carefully started to pull back Castiel’s covers until he could focus on the boxers Castiel slept in. They were easily pulled down to expose the soft swell of Castiel’s plump little ass. A sleepy mumble caught his attention, “ _Dean_?”

“Yes.” He breathed and picked up the bottle of lube before pressing it up against the tight pucker of Castiel’s hole. It squirted right inside causing Castiel to whimper at the cold, wet feel of it being squeezed directly into his ass. Dean preferred having Castiel as sloppy and wet as possible when he pushed inside. “Are you going to be my little whore tonight, Cas?” Dean squirted some lube out onto his finger and teased Castiel’s hole. “Going to take my dick in that tiny hole of yours? Let me fuck your hungry cunt till you're dripping come?”

Castiel nodded, eyes blinking, as he pushed against Dean’s finger. “Yes, Dean.” His voice was low and Dean kept his attention half on the other sounds in the house as he started to press a finger inside.

He idly wondered if his youngest brother understood how wrong others would find this. How they would say he was taking advantage of Castiel's age and his little brother-big brother hero worship.

“Make sure you’re quiet, whore.” Dean sunk his finger in to the knuckle, “We can’t have our parents knowing what a greedy little slut you are for your big brother’s fat dick.” This was a game they’d been playing for awhile. At least since he’d first noticed how tempting Castiel’s ass was when his little brother had bent over to pick something up.

Dean had told Castiel it was  _their secret_   _game_. He couldn't risk anyone finding out he was fucking his little brother and Castiel was always so eager to please.

He twisted his finger and pumped it a few times. Dean rubbed against Castiel’s prostate and smirked when Castiel moaned his name.

“I’ve never seen an ass so greedy to be filled. You’re just a warm cock-sleeve waiting for my dick to fill you.”

The second finger had Castiel gasping and his hole locking down on Dean’s fingers. “Ohhhh.”

Dean pulled his fingers out and smacked Castiel’s ass three times in rapid succession, “Quiet! You’re not getting what you want if you wake them up and I know you know the punishment for almost getting caught.”

“Sorry.” Castiel murmured and Dean pushed his fingers back inside. He focused on stretching his little brother out and listening to the way Castiel had to muffle his moans against his arm.

It took four fingers before Dean was willing to consider Castiel stretched enough for his cock. He was smaller than Dean and while Dean _loved_ having Castiel's little hole nice and tight he didn't want to tear him by shoving in too soon considering their size difference. Dean poured some more lube directly into Castiel's open, clenching hole and then into his hand before he stroked his thick cock, slicking himself up. “On your knees, whore.”

Immediately Castiel scrambled up, tan legs spread on the mattress, as he stuck his ass in the air for Dean. It was a position he'd had more than enough experience assuming once Dean taught him how he liked it. Dean used his knees to spread Castiel’s wider out onto the mattress as he shifted up behind his youngest brother. The view was beyond tempting and Dean saw no point in denying temptation as he gripped his cock and guided it right into tight heat.

Castiel released a soft, broken sound and his hole clenched up before relaxing. He wanted to slam inside. Instead Dean gripped onto Castiel and slowly pushed in.  His mouth fell open and his eyes hooded as his balls rested against Castiel’s soft, plump ass and the tightness of Castiel had him shivering in pleasure.

“Little fucking slut.” Dean groaned as he rolled his hips back and snapped them forward. His balls slapped against Castiel’s ass and the thrust had Castiel swaying. “Love taking your big brother’s dick in your slutty hole, don’t you?”

“Yes yes yes yes  _yes_!” Castiel chanted lowly, “Please Dean please.” he'd also trained Castiel in what he liked while fucking. He loved what a fast learner Castiel was.

“Nothing but a hungry cockslut. A pretty little cumbucket wanting to be fucked full.” Dean snapped his hips forward and relished the tight heat his cock repeatedly slid into. “That’s the only thing you’re good for.”

Castiel’s mattress groaned as Dean worked himself forward quicker and the headboard knocked lightly on the wall right when Castiel couldn’t hold back a particularly filthy sounding moan that Dean only encouraged when the house was empty or they were somewhere they couldn't get caught. It echoed in the room along with the sounds of rough fucking and Dean stilled.

He paused and listened. A sigh of relief almost escaped when he heard the distinct sound of their parents’ door opening. The creak had his heart pounding and Dean immediately pulled out of Castiel, threw the covers over his brother and moved to rest on the other side of the bed away from the door.

“Pretend to be asleep.” He hissed and held his breath as Castiel’s door creaked open.

From his position under the bed Dean recognized their father’s feet. They stayed there for awhile before the door shut and their dad moved back down the hall. Dean waited until he eventually heard voices, his dad saying something about him still being out and then they were going back into their room.

“You almost got us caught. You know what bad whores get don’t you?”

Castiel shifted on the bed, “Yes. I’m sorry, Dean.” His voice was low and rough.

“You have fifteen spankings coming later with a dildo in your ass.” Dean breathed and shifted, “We’re going to have to finish on the floor. Get back in position, _whore_.”

Slowly Castiel climbed off the bed giving Dean a great view of his small cock, hard and waiting for release. He had to shove Castiel’s legs wider, guided him back as he wanted him, before moving up behind Castiel. Dean didn’t waste any time before he pushed back in and set about pounding into Castiel in hard, fast strokes.

He pushed Castiel’s upper body down and braced a hand on his hip, “Such a loud little whore.” Dean breathed as he chased his release and moaned lowly. “Love taking a dick too much, don’t you?”

“Yes!” Castiel kept his voice pitched low, “Please Dean please.”

Dean rapidly thrust forward and managed to silence his own sounds of pleasure when his cock emptied into Castiel. He reached around and started jerking Castiel off in quick, sure strokes as his cock softened.

“Dean Dean Dean.” Castiel panted and tried to thrust into Dean’s hand. He came with a muffled wail that Dean _knew_  from experience was a loud, dirty sound that carried loudly when their parents were gone.

He toyed with Castiel's small cock, listening to the hitching of his breath and the whimpering Castiel released as he relished the way Castiel's hole clenched around him tightly.

"I knew the second I saw this," Dean teased the head of Castiel's cock, "That you were a perfect little bottom. Meant to take dick in your tight hole. You're going to be a popular little slut."

Castiel released another sobbing whimpering before Dean let go and shifted slightly moaning lowly when Castiel's ass squeezed him once more.

“I expect you to be loose and slick for me after you get out of school and in my bed waiting for me. I want you sitting in the center, ass flat on the bed, with the ridged black dildo from my room buried inside of you.” Dean spoke as he pulled out and got to his feet, “My whore should be ready for his punishment and to take my dick the second I get into my room tomorrow. I'll come in before you leave and cage your little dick before you go to school.”

The black dildo was one of the largest toys he'd acquired since he'd started fucking his little brother and the one that he could see poking against Castiel’s flat stomach whenever it was fully seated inside him. It wasn't simply long but very thick especially at the base once it was buried completely inside his little brother. Castiel would have to finger himself open as much as he could and use several other toys before he'd be anywhere near ready to have  _that_ toy inside him. The thought of the large gape it would have Castiel's little pink hole displaying for him had Dean stifling a groan.

It would be obscene.

Dean's softening cock slipped out of Castiel's sloppy little hole, trailing come and lube, as he admired the puffy rim and way Castiel's open hole clenched instinctively now that he was empty. He moved around to grab the fat pink butt plug he loved shoving into Castiel's plump little ass and pushed it past the rim until it popped inside, settling and keeping his release locked away.

It wouldn't do to have his parents figure out what he was doing with his little brother by finding wet spots on Castiel's bed. He hauled Castiel up and dragged him in for a kiss, touching Castiel’s naked body and tasting the lingering minty toothpaste he’d used before. “ _Dean_.” Castiel breathed when they separated.

“I bought you a ball-gag.” Dean gripped Castiel’s ass and squeezed, finger reaching out and rubbing against the plug nestled between Castiel's cheeks, “We’ll have to use that next time I come in here at night. I think we’ll use it from now on to keep those moans quiet so I can fuck you harder at night.”

“You make me feel good.” Castiel murmured, “I can’t help it.” he blinked and furrowed his brow, "And it's what you told me you wanted."

Dean smirked, “I know. I know how much you love my dick but we can’t have our parents or Sammy catching us. Remember this is our little secret. No one can know. Ever.”

 

**Author's Note:**

> A little bit different; hope some of you enjoyed this one!


End file.
